The present invention relates to cathodic sputtering apparatus and more particularly to an improved rotatable magnetron cathode.
In U.S. Pat. No. 4,356,073, issued Oct. 26, 1982, the rotatable cathode therein disclosed is mounted in an evacuable coating chamber and comprises an elongated cylindrical tubular member rotatable about its longitudinal axis and having a layer of the desired coating material, which is to be sputtered upon substantially planar substrates as they move through the coating chamber, applied directly to the outer surface thereof.
It is also stated in the patent that by applying different coating materials to different portions or segments of the outer surface of the rotatable tubular member a particular selected coating material can be brought into sputtering position. In this way, it is possible to sputter different coating materials onto the substrates from a single source.
This method of sputtering different coating materials from the same target is, however, subject to certain definite limitations. Thus, when a particular portion or segment of the coating material has been depleted the cathode must be removed from the coating chamber, the surface cleaned to remove any of the depleted coating material remaining on the cathode and a fresh coating applied.
The removal of the cathode from the apparatus, the cleaning thereof and the application of a fresh coating material is expensive and time consuming. There are increased labor costs as well as the loss of productivity of the cathode during this period. There is also the danger that the fresh coating material when applied, will overlap adjacent different coating materials. The cleaning of the cathode is necessary because the coating material is not evenly eroded and some material remains after depletion.